CN112816771A - Board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability - Google Patents
Board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability Download PDFInfo
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- CN112816771A CN112816771A CN202011621394.4A CN202011621394A CN112816771A CN 112816771 A CN112816771 A CN 112816771A CN 202011621394 A CN202011621394 A CN 202011621394A CN 112816771 A CN112816771 A CN 112816771A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
Abstract
The invention discloses a board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability, wherein a PCB is welded with a precision amplifier for acquiring direct-current quantity, and the PCB is also welded with an EMC protection circuit and a filter circuit, the EMC protection circuit is used for processing input signals and transmitting stable signals within the input range of the precision amplifier to a precision amplifier circuit; the filter circuit is used for filtering the power supply accessed to the precision amplifier circuit; the PCB comprises a strong current part and a weak current part, wherein the strong current part is used for welding the EMC protection circuit, and the weak current part is used for welding the filter circuit; the strong current part and the weak current part are in accordance with the safety distance. The advantages are that: the invention can realize small-sized packaging and can be compatible with common mutual inductor packaging; the single-board transformer can be used as a common transformer without changing the single board; the module is additionally provided with a protective circuit on the periphery of the device, and the electromagnetic protection capability is improved.
Description
Technical Field
The invention relates to a board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability, and belongs to the technical field of circuits.
Background
The device or the single board (the direct current collecting device or the board card) carries out direct current voltage or current sampling through the external signal isolation transmitter module, although the output precision is high, the temperature drift is low, the EMC protection level is high, the voltage and current measurement range is realized only by replacing the isolation transmitter module, and the single board does not need to be changed. However, the external signal isolation transmitter module is often huge in size, and the isolation transmitter module needs to be installed by additionally increasing the space area outside the device, so that the cost is increased, and the difficulty of installation, use and maintenance of the device is increased under the condition that some space is limited. Meanwhile, the external module needs to communicate with the device through RS485/RS232, and a communication interface of the device/single board needs to be occupied. And the external module still needs to increase independent power supply and give its power supply, has increased cost and wiring degree of difficulty.
The scheme for realizing direct current acquisition by using a precision amplifier device on the single board in cooperation with simple protection and resistance voltage division has small volume and excellent precision and temperature drift characteristics. However, the electromagnetic compatibility of the high-precision isolation amplifier is weak, and the high-precision isolation amplifier can only reach B level in static discharge, rapid transient pulse immunity test and lightning surge immunity test. With the continuous improvement of the quality system in China, the electromagnetic compatibility detection of equipment, particularly power equipment, needs to reach A level through the standard, and during an electromagnetic compatibility (EMC) experiment, the damage of the whole device is caused by the insufficient anti-interference capability of a precision amplifier. In addition, the direct current quantity measured externally can be various direct current voltage signals such as 4-20 mA, 0-10V, 0-100V, 0-200V and the like, selective welding and adaptation are needed to be carried out on devices (such as resistors) on a single plate according to the direct current quantity type measured by each channel during specific engineering, and wiring and engineering maintenance are not facilitated by the scheme that a precise amplifying device is directly welded and welded on the single plate and the resistors are divided.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability.
In order to solve the technical problems, the invention provides a board-level high-precision isolation direct current voltage and current acquisition module with high protection capability, which comprises a PCB board, wherein a precision amplifier for acquiring direct current quantity is welded on the PCB board,
the PCB is also welded with an EMC protection circuit and a filter circuit, the EMC protection circuit is used for processing input signals and transmitting stable signals within the input range of the precision amplifier to the precision amplifier circuit; the filter circuit is used for filtering a power supply accessed to the precision amplifier circuit;
the PCB comprises a strong current part and a weak current part, wherein the strong current part is used for welding the EMC protection circuit, and the weak current part is used for welding the filter circuit; the strong current part and the weak current part are in accordance with the safety distance.
Further, the EMC protection circuit includes:
a voltage dependent resistor for discharging most of the energy when the input signal suddenly applies a voltage exceeding the input range of the precision amplifier,
a resistor for limiting the current and dividing the voltage,
transient suppression diodes for ensuring that the input voltage is not higher than its nominal clamp value in the event that voltages exceeding the input range of the precision amplifier are applied more permanently.
Further, the EMC protection circuit includes a voltage dependent resistor RV1, a resistor DR1, a resistor DR2, a transient suppression diode TVS1, a capacitor CY1, a capacitor CY2, and a capacitor C3;
one end of the capacitor CY2 is grounded, and the other end of the capacitor CY2 is respectively connected with one end of the piezoresistor RV1, one end of the resistor DR2, one end of the transient suppression diode TVS1, one end of the capacitor C3, the negative end of the signal input of the precision amplifier and the negative end of the signal input;
the signal input positive terminal of the precision amplifier is respectively connected with the other end of the capacitor C3, the other end of the transient suppression diode TVS1, the other end of the resistor DR2 and one end of the resistor DR 1;
the other end of the resistor DR1 is respectively connected with one end of a capacitor CY1, the other end of a piezoresistor RV1 and the positive end of signal input;
the other terminal of the capacitor CY1 is connected to ground.
Further, the filter circuit comprises a capacitor C1 and a capacitor C2, wherein the capacitor C1 and the capacitor C2 are connected between the positive and negative end interfaces of the power supply of the precision amplifier and the power supply in parallel.
Furthermore, the positive end of the analog signal output of the precision amplifier and the negative end of the analog signal output are connected to the single board.
Further, the safety distance is at least 4 mm.
Furthermore, the PCB is packaged through a shell, and the packaged PCB comprises 4 leads and 3 contact pins;
wherein, 2 lead wires are connected with external direct current voltage or current signals needing sampling, and the other two lead wires are connected with direct current 5V and GND on a single board as a power supply of the module;
one end of the 1 st contact pin is connected with an analog signal output positive terminal, and the other end of the 1 st contact pin is connected with a signal input positive terminal of the single board;
one end of the 2 nd contact pin is connected with the negative end of the analog signal output, and the other end is connected with the negative end of the signal input of the single board;
the 3 rd pin is connected with the external chassis ground or the earth ground of the single board.
Furthermore, hot melt adhesive is added when the PCB is packaged, so that the insulation distance between devices on the circuit board and each pin on the precision amplifier is increased.
The invention achieves the following beneficial effects:
the invention can realize small-sized packaging and can be compatible with common mutual inductor packaging; the single-board direct current voltage switching circuit can be used as a common transformer, and can switch various direct current voltage signals of 4-20 mA, 0-10V, 0-100V, 0-200V and the like only by replacing the module without changing any single board.
The module has increased the peripheral protective circuit of device, including TVS pipe and voltage dependent diode, the strong and weak electricity of whole circuit board is divided according to the ann rule distance strictly to the alternating current volume output signal after avoiding external input to cause the interference, even punctures the device and causes the device to damage.
Drawings
Fig. 1 is a schematic circuit diagram of the present invention.
Detailed Description
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in figure 1, a board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability adopts a sampling principle based on the use of a high-precision low-temperature drift precision amplifier device and the matching of resistance voltage division to realize sampling. Meanwhile, the scheme has high requirement on the resistance precision of the resistor, a high-precision resistor needs to be used, and after the high-precision resistor is adopted, the sampling precision can reach two thousandths.
U1 is a precision amplifier device with high precision, low temperature drift and complete isolation, and is a main device for realizing direct current acquisition. The device has pins 1 and 2 as signal output, pins 3 as gain regulation, pins 8 and 9 as signal input, pins 10 and 11 as power output, pins 15 and 16 as zero regulation, and pins 17 and 18 as positive and negative power supplies. The input voltage of a signal input end of a device is controlled by adjusting the resistance values of two high-precision resistors DR1 and DR2 and selectively welding, the signal output end of the device is connected into an analog digital conversion chip or an analog digital conversion channel of a single chip microcomputer/processor to be subjected to value taking, and conversion is carried out according to an input range and a voltage proportion to obtain a sampling value, so that various direct current voltage signals of 4-20 mA, 0-10V, 0-100V, 0-200V and the like can be acquired.
In the aspect of EMC protection of a circuit, because the electromagnetic compatibility of the high-precision isolation amplifier is weak, the device cannot pass the electromagnetic compatibility experiment, and special treatment of an external protection circuit and a module is indispensable.
An externally input direct current input signal firstly needs to pass through a piezoresistor RV1, wherein the piezoresistor is a resistor device with nonlinear volt-ampere characteristics and is mainly used for clamping voltage when a circuit bears overvoltage and absorbing redundant current to protect a sensitive device. The function of the voltage dependent resistor RV1 is that when a large voltage is suddenly applied to an external input signal (such as a lightning surge), the current flowing through the voltage dependent resistor increases sharply, so that most energy is discharged from RV1, and a subsequent circuit is protected. The selection of the resistors DR1, DR2 needs to take into account not only the accuracy thereof, but also whether the power thereof can meet the requirements of the circuit under normal and overvoltage conditions, and at least a 3-5 times margin is left to prevent overheating and burning. When the transient suppressor diode is subjected to a high-energy transient overvoltage pulse, the working impedance of the transient suppressor diode can be immediately reduced to a very low conduction value, a large current is allowed to pass through the transient suppressor diode, and the transient suppressor diode clamps the voltage to a preset level, so that precise components in an electronic circuit are effectively protected from being damaged. The purpose of adding the transient suppression diode (TVS1) to the signal input end of the high-precision isolation amplifier is to instantly conduct the leakage energy when a high-energy pulse is higher than the signal input allowable range of the high-precision isolation amplifier, thereby protecting the high-precision isolation amplifier. The large and small capacitors provide a path for high-frequency alternating current signals and harmonic waves, have a certain filtering function, and protect a power supply and an integral circuit of the device from being influenced by high-frequency alternating current quantity signals and high-frequency word harmonic waves.
The EMC protection circuit comprises a voltage dependent resistor RV1, a resistor DR1, a resistor DR2, a transient suppression diode TVS1, a capacitor CY1, a capacitor CY2 and a capacitor C3; (CY 1, CY2 is a safety Y capacitor which plays a role in inhibiting common mode interference, a capacitor C3 is a multilayer ceramic chip capacitor which forms RC filter with a front-end resistor to play a role in inhibiting differential mode interference);
one end of the capacitor CY2 is grounded, and the other end of the capacitor CY2 is respectively connected with one end of the piezoresistor RV1, one end of the resistor DR2, one end of the transient suppression diode TVS1, one end of the capacitor C3, the negative end of the signal input of the precision amplifier and the negative end of the signal input;
the signal input positive terminal of the precision amplifier is respectively connected with the other end of the capacitor C3, the other end of the transient suppression diode TVS1, the other end of the resistor DR2 and one end of the resistor DR 1;
the other end of the resistor DR1 is respectively connected with one end of a capacitor CY1, the other end of a piezoresistor RV1 and the positive end of signal input;
the other terminal of the capacitor CY1 is connected to ground.
The filter circuit comprises a capacitor C1 and a capacitor C2, wherein the capacitor C1 and the capacitor C2 are connected between the positive and negative end interfaces of the power supply of the precision amplifier and the power supply in parallel. C1 and C2 are two ceramic chip capacitors with one large ceramic chip capacitor and one small ceramic chip capacitor connected in parallel, and have a filtering function, wherein the large ceramic chip capacitor filters low-frequency interference, and the small ceramic chip capacitor filters high-frequency interference, so that a power supply is smoother.
J3 is the earth, J4 is the analog signal output positive terminal and J5 is the analog ground, J1 is the positive and negative terminals of the power supply of the precision amplifier on CON2, J2 is the signal input positive and negative terminal.
When the instantaneous high energy pulse is higher than the signal input allowable range of the high-precision isolation amplifier, RV1 provides the first-stage protection of transient voltage, the clamping action of a voltage dependent resistor prevents most transient voltage from being conducted to the output end in the very short dynamic high-voltage transient process, C3 is charged to the voltage value capable of enabling TVS1 to be conducted under the condition of more lasting stress, and TVS1 can ensure that the input voltage is not higher than the rated clamping value of the TVS 1.
Except for the addition of a protective circuit on the periphery of a device, the strong current and the weak current of the whole circuit board are strictly divided according to the safety distance so as to prevent an alternating current voltage and current signal input from the outside from interfering an alternating current output signal after isolation and even break down the device to cause device damage. Therefore, the areas where the strong and weak electric signals on the PCB are located are clearly divided, the wiring is more convenient by mainly using a surface mounted device, and the safety distance also reaches more than 4 mm. In addition, the strong and weak electric isolation distance of the high-precision isolation amplifier is not enough to meet the requirement of A-level safety distance in the rapid transient pulse immunity and lightning surge immunity test. Therefore, the pads which are not used in the device need to be hollowed, and pins on the device also need to be cut off, and the safety isolation distance between the strong current and the weak current of the high-precision isolation amplifier can be artificially increased by the method. In addition, a plurality of hot melt adhesives are added in the module by plastic package of the circuit board, and the insulation distance between the device and each pin is also increased, so that the module can finally meet the requirements of 8kV contact discharge voltage, 4kV rapid instantaneous pulse anti-interference test and 4kV and above A-level protection level of lightning surge anti-interference test.
The invention has the advantages that:
1. the encapsulation is standardized, plug-and-play, need not to increase power supply and need not to change other plates.
The module is small in specification, the shell is packaged by 31mm or 24mm, the height is 3mm, and the package can be compatible with common mutual inductors; in the aspect of external interfaces, firstly, the module is externally provided with 4 leads, 2 leads are connected with external direct current voltage or current signals needing to be sampled, and the other two leads are connected with direct current 5V and GND on the internal single board to serve as a power supply of the module, so that the module does not need to be additionally provided with an independent power supply to supply power for the module, and power taking is convenient.
The connection mode is flexible and convenient, the interface definition is standardized and is compatible with the package and the interface definition of a common mutual inductor, so that the module can be used as the common mutual inductor, and the switching of various direct current voltage signals such as 4-20 mA, 0-10V, 0-100V, 0-200V and the like can be completed only by replacing the module without changing any single board.
2. The protection level is high, and the electromagnetic compatibility protection level of the scheme reaches A level.
The module has increased the peripheral protective circuit of device, including TVS pipe and voltage dependent diode, the strong and weak electricity of whole circuit board is divided according to the ann rule distance strictly to the alternating current volume output signal after avoiding external input to cause the interference, even punctures the device and causes the device to damage. Therefore, the areas where the strong and weak electric signals on the PCB are located are clearly divided, the wiring is more convenient by mainly using a surface mounted device, and the safety distance also reaches more than 4 mm. In addition, the strong and weak electric isolation distance of the high-precision isolation amplifier is not enough to meet the requirement of A-level safety distance in the rapid transient pulse immunity and lightning surge immunity test. Therefore, the pads which are not used in the device need to be hollowed, and pins on the device also need to be cut off, and the safety isolation distance between the strong current and the weak current of the high-precision isolation amplifier can be artificially increased by the method. In addition, a plurality of hot melt adhesives are added in the module by plastic package of the circuit board, and the insulation distance between the device and each pin is also increased, so that the module can finally meet the requirements of 8kV contact discharge voltage, 4kV rapid instantaneous pulse anti-interference test and 4kV and above A-level protection level of lightning surge anti-interference test.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (8)
1. A board-level high-precision isolation direct current voltage and current acquisition module with high protection capability comprises a PCB board, wherein a precision amplifier for acquiring direct current is welded on the PCB board,
the PCB is also welded with an EMC protection circuit and a filter circuit, the EMC protection circuit is used for processing input signals and transmitting stable signals within the input range of the precision amplifier to the precision amplifier circuit; the filter circuit is used for filtering a power supply accessed to the precision amplifier circuit;
the PCB comprises a strong current part and a weak current part, wherein the strong current part is used for welding the EMC protection circuit, and the weak current part is used for welding the filter circuit; the strong current part and the weak current part are in accordance with the safety distance.
2. The board-level high-precision isolation direct-current voltage and current collection module with high protection capability of claim 1,
the EMC protection circuit includes:
a voltage dependent resistor for discharging most of the energy when the input signal suddenly applies a voltage exceeding the input range of the precision amplifier,
a resistor for limiting the current and dividing the voltage,
transient suppression diodes for ensuring that the input voltage is not higher than its nominal clamp value in the event that voltages exceeding the input range of the precision amplifier are applied more permanently.
3. The board-level high-precision isolation direct-current voltage and current collection module with high protection capability of claim 2,
the EMC protection circuit comprises a voltage dependent resistor RV1, a resistor DR1, a resistor DR2, a transient suppression diode TVS1, a capacitor CY1, a capacitor CY2 and a capacitor C3;
one end of the capacitor CY2 is grounded, and the other end of the capacitor CY2 is respectively connected with one end of the piezoresistor RV1, one end of the resistor DR2, one end of the transient suppression diode TVS1, one end of the capacitor C3, the negative end of the signal input of the precision amplifier and the negative end of the signal input;
the signal input positive terminal of the precision amplifier is respectively connected with the other end of the capacitor C3, the other end of the transient suppression diode TVS1, the other end of the resistor DR2 and one end of the resistor DR 1;
the other end of the resistor DR1 is respectively connected with one end of a capacitor CY1, the other end of a piezoresistor RV1 and the positive end of signal input;
the other terminal of the capacitor CY1 is connected to ground.
4. The board-level high-precision isolation direct-current voltage and current collection module with high protection capability of claim 1, wherein the filter circuit comprises a capacitor C1 and a capacitor C2, wherein the capacitor C1 and the capacitor C2 are connected in parallel between a positive-negative terminal interface of a power supply of the precision amplifier and the power supply.
5. The board-level high-precision isolated DC voltage and current collection module with high protection capability of claim 1, wherein the positive end of the analog signal output and the negative end of the analog signal output of the precision amplifier are connected to the single board.
6. The board-level high-precision isolated DC voltage and current collection module with high protection capability of claim 1, wherein the safety distance is at least 4 mm.
7. The board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability according to claim 3, wherein the PCB is packaged by a shell, and the packaged PCB comprises 4 leads and 3 pins;
wherein, 2 lead wires are connected with external direct current voltage or current signals needing sampling, and the other two lead wires are connected with direct current 5V and GND on a single board as a power supply of the module;
one end of the 1 st contact pin is connected with an analog signal output positive terminal, and the other end of the 1 st contact pin is connected with a signal input positive terminal of the single board;
one end of the 2 nd contact pin is connected with the negative end of the analog signal output, and the other end is connected with the negative end of the signal input of the single board;
the 3 rd pin is connected with the external chassis ground or the earth ground of the single board.
8. The board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability of claim 7, wherein a hot melt adhesive is added during the packaging of the PCB board, so as to increase the insulation distance between devices on the circuit board and each pin on the precision amplifier.
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| CN202011621394.4A CN112816771A (en) | 2020-12-30 | 2020-12-30 | Board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability |
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| CN202011621394.4A CN112816771A (en) | 2020-12-30 | 2020-12-30 | Board-level high-precision isolation direct-current voltage and current acquisition module with high protection capability |
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| CN103887965A (en) * | 2012-12-19 | 2014-06-25 | 研祥智能科技股份有限公司 | Power supply design circuit with high-level EMC and safety regulation performance |
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